In a conventional descent device which is also used together with a rope, said rope is wound either on a shaft or on an S-shaped groove or the like. A man than hangs down from the device, whilst grasping said rope, and travels down by loosening the underside rope provided through the device. Accordingly, if someone on the ground should pull the rope by mistake, the descent movement will be discontinued. Then, even if it is necessary to change the descent position to avoid dangers or obstacles when the device is used as a means of escape, rescue personnel on the ground cannot change the descent position. Furthermore, as a subsequent person cannot descent until the rope is loosened after the former person completely touches down on land, the efficiency of escape in emergency is not very satisfactory.
If, to regulate the speed of descent, a person directly grasps the underside rope of the device, and if that person then becomes unconscious as he firmly grasps the underside rope of the device during a falling movement, no one can then bring him down, and subsequent descending movements will not be possible. Further, no one can approach an unconscious person, when descending to rescue him. On the contrary, if a person releases his hand from said rope, he will be killed by the resultant drop.
Furthermore, the higher the escape position becomes, the longer the rope become and the heavier the weight of said rope itself becomes. Therefore, it will be difficult to descend by loosening the rope, when the weight of said rope is great. Thus, it is impossible to use such a conventional escape or descent device for escape from an extremely high position.
There are also known other devices such as those of wellbucket type, by which alternate descents are available, in which a block having a brake is employed. However, this type of descent device is large in size, and expensive in production and installation. Furthermore, said type of device cannot take down several persons at the same time.